Abstract

Many crystalline laser hosts have been studied with Tm-Ho co-doping where the trivalent Tm ion serves as sensitizer (conveniently pumped near 800 nm by laser diodes) and the trivalent Ho ion, excited by energy transfer, lases on its 2-μm ⁵I₇→⁵I₈ transition. Little attention has been paid so far, however, to the monoclinic double tungstate crystals although it is known that they exhibit maximum absorption and emission cross sections and minimum concentration quenching. Continuous-wave (CW) lasing of Ho³⁺ with Ti:sapphire laser pumping was achieved for the first time in Tm,Ho:KY(WO₄)₂ [1] and these results were later extended to mode-locking. Almost simultaneously we grew and investigated the spectroscopic properties of the related Tm,Ho:KLu(WO₄)₂ (Tm,Ho:KLuW) [2]. Under Ti:sapphire laser pumping, however, few different dopant combinations and output couplers indicated dual wavelength operation (simultaneous lasing of Tm and Ho) and the maximum output power of the Ho laser reached only 156 mW [3]. Here we demonstrate an improvement by a factor of >2, both in terms of slope efficiency and output power of the CW Tm,Ho:KLuW laser, oscillating solely at 2060 nm.

© 2013 IEEE